Digit_(anatomy)

Digit (anatomy)

A digit is one of several most proximal parts of a limb, present in many vertebrates.

Human digits

Humans normally have five digits on each extremity. Each digit is formed by several bones called phalanx, surrounded by soft tissues. Every human finger normally has a nail on its distal phalanx.

Lingusitic differences

In English, digits of the hand are called fingers, while foot digits are called toes. In many other languages, e.g. Spanish, Russian, Polish, Portuguese, Italian, there are no specific one-word names for fingers and toes; these are called "digit of the hand" or "digit of the foot" instead.

Evolution

Recent paleontologic research has dismissed earlier assumptions hands and feet evolved out of nowhere in the first primitive land-living animals. A three-dimensional reconstruction of a Panderichthys, a coastal fish from the Devonian period 385 million years ago, showed these animals had many of the bones present in the modern human arms, including "radial" bones similar to rudimentary fingers but concealed in the arm-like base of the fins. As tetrapods originated, the study suggests, the outermost part of the fins were lost and eventually replaced by the primitive digits. However, the Tiktaalik, often regarded as the missing link between fishes and land-living animals, had stubby leg-like limbs missing the finger-like radial bones found in the Panderichthys. While this could simply be an evolutionary step backward, conclusions from the new findings still need be confirmed. They seem, however, to corroborate that at least precursors to modern digits were present in early fishes.